A high pressure pump for pressurizing fuel to be supplied to an internal combustion engine has been conventionally known. The high pressure pump may include an electromagnetic valve for controlling operation of a suction valve. The suction valve is configured to open and close a supply passage connected to a pump chamber in which the fuel is pressurized.
For example, a patent document 1 (JP 2012-82809 A) discloses an electromagnetic valve disposed in a high pressure pump. The electromagnetic valve includes a movable core reciprocatably disposed in a core chamber and a valve stem fixed to the movable core. The valve stem is pressed toward a pump chamber by biasing force of a spring a suction valve to open a supply passage. When the movable core is magnetically attracted toward a stator core, the valve stem releases pressure force against the suction valve.
However, in the electromagnetic valve disclosed in the patent document 1, surfaces of the movable core and the stator core may be eroded due to cavitation generated by fuel pressure fluctuation between the movable core and the stator core when the movable core reciprocates in the core chamber.
Generally, the movable core and the stator core are made of a soft magnetic material and thus may be easily susceptible to the erosion. When the surfaces of the movable core and the stator core are eroded, a gap between the movable core and the stator core may become larger. Therefore, a response time required to complete the operation of the movable core after applying electricity to the electromagnetic valve may become longer.
Further, foreign materials resulting from the erosion of the movable core and the stator core may be mixed with the fuel, and hinder operation of the high pressure pump.